This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. This project will identify types and levels of polybrominated diphenyl ether (PBDE) congeners in zooplankton and muscle tissue of forage fish species from two Southeast Alaska estuaries, one that is subject to localized and another that is subject to remote sources of PBDEs. Extracts from whole bodies of zooplankton and from tissue samples from forage fish collected from the two estuaries will be analyzed for PBDE levels and congener distribution. The concentration data will be used in conjunction with PBDE levels previously determined in sediments and bivalves from the same estuaries to determine trophic magnification factors (TMF). Analysis of trophic level variations in congener distributions and concentrations will indicate how the PBDE congener distributions change as they move through environmental matrices. TMF data will also be used to explore the toxicity of environmentally relevant mixtures of PBDEs. Toxic equivalency factors (TEFs) will be used to estimate the total toxicity equivalence (TEQ) of the PBDE congener mixtures associated with each trophic level. A limited number of TEF values for PBDE congeners are available in the literature so this study will utilize TEF values for structurally analogous chlorinated compounds when necessary. The TEQ value indicates the toxicity of mixtures of related substances and will contribute valuable insight regarding threats to commercial fish and wildlife stocks from synergistic effects among PBDE congeners. The objective of this study is to determine PBDE congener distributions and concentrations in several trophic levels found in the Lemon Creek and the Peterson Creek estuaries of Southeast Alaska. These data will be used to evaluate 1) trophic magnification factors for PBDE congeners and 2) to assess the toxicity of environmental mixtures that result from the attenuation of PBDEs under environmental conditions and 3) to assess the threat posed by remote and local PBDE sources to human health.